Radiation source and method



Y. Mgy 27, y1969 D. G. vvA'N ORNUM ETAL 3,447,013

RADIATION SOURCE AND'METHOD med .June 2o. lwas United States Patent O 3,447,013 RADIATION SOURCE AND METHOD Delbert G. Van Ornum, Newport Beach, and Ronald E.

Sheets, Westminster, Calif., assignors to Giannini Scientific Corporation, Amityville, N.Y., a corporation of Delaware Filed June 20, 1966, Ser. No. 558,904 Int. Cl. H01j 61/52 U.S. Cl. 313-12 26 Claims ABSTRACT OF THE DISCLOSURE A gas-vortex stabilized radiation source and method in which a major amount of gas is drained from the peripheral regions of the are chamber in order to maintain the window relatively cool, only a minor amount of the gas draining through the central or axial region of the chamber. In accordance with another major aspect of the method and apparatus, the operation is readily changed between that causing a relatively constricted discharge (producing radiation high in the ultraviolet), and that causing a relatively unconstricted discharge (producing radiation relatively high in the infrared), by manipulating a valve means adapted to change the drainage of gas from the discharge chamber.

This invention relates to a radiation or light source, and to a method of generating light and similar forms of radiation.

Radiation or light sources wherein the electrical discharge is stabilized by means of vortically-flowing gas have in recent years become progressively more important for both military and commercial purposes. One major problem relative to such sources has involved cooling of the light-transmissive window or envelope. To augment the window-cooling action effected by the vortically iiowing gas at the peripheral regions of the arc chamber, it has previously been proposed to cool the exterior window surface by circulating thereover a ow of gas, water or other fluid. We have now discovered that, instead of or in addition to such cooling of the exterior window surface7 a highly eifective window-cooling action may be achieved by drastically increasing the flow of gas through the arc chamber itself, and draining only a minor proportion of such gas adjacent t-he axis of the chamber for purposes of stabilizing and constricting the arc or spark. A major portion of such vortically-owing gas is drained from the peripheral regions of such chamber, without ever appreaching the arc for heating thereby. Because of the relative coolness and high mass flow of the peripherallydrained gas, an effective window-cooling action is achieved. Surprisingly, such draining of massive amounts of gas from the peripheral regions of the chamber does not prevent or interfere with eifective vortex-stabilization of the discharge.

In previous vortex-stabilized radiation sources, it was known to drain a small Ipercentage of the vorticallyflowing arc gas, from the periphery of the arc chamber, for the purpose of removing particles of an additive which was purposely injected into the arc in order to change the spectral emission pattern thereof. However, insofar as the present inventors are aware, it was not known to drain gas peripherally from sources wherein no additive is injected. Furthermore, it was not known to drain major amounts of gas from the periphery of the arc chamber.

Another problem of the prior art involved changing the spectral emission pattern in a rapid and simple manner, without employing additives and without changing the power level or the gas pressure (or gas composition) in the system. The present inventors have discovered that 3,447,013 Patented May 27, 1969 lCe drained from the peripheral region of the arc chamber for purposes including cooling of the envelope.

A further object is to provide a vortex-stabilized radiation source and method wherein various gas flows may be readily regulated in order to achieve different arc characteristics and thus diierent spectral emission patterns.

A further object is to provide a recirculating vortexstabilized radiation source wherein the emission may be changed from largely ultraviolet to largely infrared witihout changing the gas pressure or composition in the system, or the power level, and without using additives.

These and other objects will become apparent from the following detailed description taken in connection with the accompanying drawing in which:

FIGURE l is a schematic longitudinal central sectional view of a radiation source constructed in accordance with the present invention,

FIGURES 2 and 3 are sectional views taken, respectively, on lines 2--2 and 3 3 of FIGURE 1; and

FIGURE 4 is an enlarged fragmentary section view on line 4-4 of FIGURE 3.

Referring to the drawing, the radiation or light source is illustrated schematically to comprise rst and second elongated metal electrodes 10 and 11, respectively, which are suitably mounted coaxially of each other and in axially-spaced relationship. Mounted sealingly around the arcing end portions (which may be formed, for example, of tungsten or thoriated tungsten) of electrodes 10 and 11, and concentrically relative to the common axis of such electrodes, are inner and outer tubular envelopes 12 and 13, respectively, formed of light-transmissive or transparent material. The mounting means for the electrodes and for the envelopes include end elements 14 and 15 which are suitably adapted, as with sealing and other devices, to close the space around the arcing end portions of the electrodes and to close the ends of the annulus 16 between the envelopes. The space around the arcing end portions is designated 17 and comprises the arc or discharge chamber.

The end portion of electrode 10 is shown as being generally conical and surrounded by a 4generally conical shroud 19 Vthrough which some of the gas drained from arc chamber 17. Such gas flows through a plurality of radial passages 20 (FIGURE 2) and hence 'into a gas-outlet conduit 21 for transmission to a suitable heat exchanger 22 (adapted to cool the gas) and recirculation pump 23. From the outlet side of the pump, the gas flows `into one end of annulus 16 and thence through such annulus and through ya plurality of gas-inlet passages 24 (FIGURES 3 and 4) into the peripheral portion of Aarc cham-ber 17, such gas-inlet passages being provided through end element 15. The passages 24 are generally tangentially arranged relative to the arc ychamber 17, so that the entering gas flows vortically in 4such chamber prior to draining therefrom. As best shown lin FIGURE 4, the passages 24 extend not only tangentially but also axially, oausing the entering gas to follow a helical path.

A suitable power source 26, for example, a D.C. source, is electrically connected to the end elements 14 and 15 (which are formed of metal) and thus to the electrodes.

An arc 27a or 27h may thus be maintained axially of chamber 17 and between the electrodes. Such aro, which is normally a high-current arc, is stabilized and constricted by the vortioally-flowing gas in chamber 17. Electrode should be the cathode. In certain radiation sources, the power source 26 may be a pulse source, such as a capacitor bank, so that the electrical discharge will be a spark instead of an arc.

Suitable Water conduits W (FIGURE l) are shown as associated with electrode 10 to effect water cooling thereof. Similarly, the electrode 11 may be continuously water cooled.

The gas passed tangentially into the arc chamber 17 may comprise xenon, argon, krypton, etc., lat relatively high pressures.

The vortically-owing gas drains not only through shroud 19 but also through at least one, and preferably several, additional gas-outlet means. Thus, electrode 11 is provided with an axial bore 28 which communicates (for example, through the reduced-diameter port or opening 31) with the axial region of arc chamber 17. Bore 28 also communicates through a conduit 34 with the aboveindicated recirculation conduit 21.

In accordance with the present invention, gas-outlet means 40 are provided and are capable of draining a major proportion of the vortically-flowing gas from chamber 17 at the peripheral region thereof, adjacent the interior surface of inner envelope 12. The illustrated drainage means comprise four passages extended through end element 14 from chamber 17 to a header element 41, the latter communicating through a conduit 42 with the recirculation conduit 21.

Valve means are provided to -control the gas flows though the various conduits in order to regulate the proportionate flows as well as the total flow. Thus, a valve 43 is provided in conduit 34, a valve 46 in conduit 21 (upstream of the junction thereof with any other conduit), a valve 47 in conduit 42, and a valve 48 in conduit 21 at a region thereof relatively adjacent heat exchanger 22. Such valves may be remote-operated, automatic, etc., and adapted simultaneously to achieve predetermined settings.

The pressure of the gas in arc chamber 17 may be, for example, on `the lorder of 12 to 20 atmospheres or higher. The magnitude of the current which flows between the electrodes 10 and 11 may be, for example, on the order of 400 amperes or higher. Also, of course, certain lower currents -and pressures may be employed. The high currents may be utilized despite the fact that the apparatus is relatively small. Thus, for example, the inner diameter of envelope 12 may be, for example, on the order of 1% inches. The gap between electrodes 10 and 11 may be, for example, 1() to l5 millimeters, although much higher gaps (such as to 30 millimeters) may also be employed.

Description 0f method In performing the method of the invention, let it first be assumed that it is desired to generate a highly-constricted arc such as is illustrated in FIGURE l at 27a. Such an arc has been found to produce a spectral emission pattern which is high in the ultraviolet range. To achieve such constriction, valve 47 may be shifted to closed condition so that ow through peripheral outlets 40 is blocked.

The -system being filled with xenon or other desired gas under relatively high pressure, pump 23 is set into operation to effect circulation of gas from the pump into annulus 16, thence through tangential inlet passages 24 into the region of arc chamber 17 around the anode 11, and thence to the vicinity of the arc chamber between the electrodes. Valves 43 and 46 should be so adjusted that ia major amount of gas drains from the arc chamber through the annulus defined within shroud 19, such gas flowing through passages 20 into conduit 21 and thus back to the heat exchanger 22 and pump 23. A minor amount of `gas is caused to drain through opening 31 and passage 28 to conduit 34 also leading to the heat exchanger and pump. Thus, for example, the valve 43 may be so set that approximately percent of the gas Within arc chamber 17 drains through passages 20-21 and approximately l0 percent through passages 31 and 28.

An electrical discharge is then initiated between electrodes 10 and 11, being indicated at 27a in FIGURE l. The discharge may be a steady-state arc, or a pulse or spark discharge. The `discharge 27a follows a straight-line path through the canal defined within the vortioally-owing gas, and is highly constricted as illustrated.

In the indicated mode of operation, a major amount of gas is drainedthrough a shroud 19 around the cathode 10, and -a minor amount is drained through passages 31 and 28. It has been found that this gas-flow pattern produces an arc 27a which is surprisingly stable and efficient, and which produces along electrode life. The gas which drains through the central opening in the anode 11 is effective in producing `constriction and stabilization of the electrical discharge without, however, causing the discharge to extend for a substantial distance into the anode 11. The latter is important since the region of the discharge within the anode 11 is relatively wasted in that the light generated thereby is shielded by the wall of the anode passage.

The portion of the vortically-flowing gas which discharges through the shroud 19 is important for a number of reasons, including the fact that the area at which the arc contacts the tip of lche cathode 10 is lgreatly increased, with consequent increased stability and lengthened electrode life. Furthermore, the portion of such gas which discharges through the annulus within shroud 19 is effective in producing stabilization of the discharge.

When it is desired to shift from the above-described constricted mode of operation producing the relatively smalldiameter arc 27a (with consequent high-ultraviolet emission) to a less constricted `mode of operation which produces a relatively large-diameter arc or electrical discharge, indicated at 271;, valves 43, 46 and 47 are adjusted in such manner that a very large proportion of the gas drains from chamber 17 through the peripheral drain passages 40. Only a small proportion of the gas then drains through the central opening 31 in anode 11, such proportion draining through port 31 being preferably much smaller than the pro-portion draining through the shroud. It is emphasized that the above-indicated shift `from the highly-constricted mode to the less constricted mode `may thus lbe achieved instantaneously, by merely adjusting valves.

As lan example of the less constricted mode (producing a discharge such as 27b) the various valves may be so adjusted that approximately 70 percent of lche gas introduced into arc chamber 17 drains through the peripheral openings 40, Whereas only about 2 percent drains through the `anode opening 31. The remainder, or approximately 28 percent, flows through the annulus around cathode 10.

The relatively large-diameter electrical discharge 2711 is surprisingly well stablized and, very importantly, produces an emission pattern which is markedly different from that produced by the smaller-diameter or more constricted arc or discharge 27a. Stated more definitely, the emission produced by the large-diameter discharge 27b is much ymore in the nature of infrared, whereas (as stated above) that produced by more constricted discharge 27a is more in the nature olf ultraviolet.

It is pointed out that various modes of operation may be obtained, intenmediate to those indicated above relative to the discharges 27a and 27b, tby adjusting the valves 43, 46 and 47 to various intermediate settings. In one advantageous setting, producing a relatively constricted discharge, approximately 70 percent of the gas in chamber 17 flows through shroud 19, l0 percent through opening 31, and 20 percent through passages 40.

It is an important feature that the highly-constricted mode and approximations thereof may also be achieved when valve 47 is open, even `fully-open. This is accomplished by increasing the total mass flow through arc chamber 17 until the volumes drained through shroud 19 and anode 11 approximate the volumes drained therethnough with valve 47 closed as indicated above. Such increase in total mass ow may be effected by increasing the number or diameters of gas-inlet passages 24, by increasing the pressure differential, by adjusting valve 48 to a more open condition, etc.

It will therefore be understood that the highly-constricted mode (producing a 'discharge such as 27a) is achieved by causing 1a sufficiently large drainage of gas at a region or regions relatively near the axis of chamber 17, whether or not there isa large drainage from the periphery of such chamber. The less constricted mode (producing a discharge such as 27b) is achieved by reducing sufficiently the drainage of gas from axial regions of the chamber 17, and effecting a large drainage from chamber portions remote from the axis.

Thus, in both the highly-constricted and slightly-constricted modes, a large proportion of the gas may be caused to flow along relatively short helical paths from inlets 24 to peripheral outlets 40, such gas passing closely adjacent the inner surface of envelope 12 so that large quantities of heat are absorbed thereform. Localized stagnant or hot regions, for example radially-outwardly of the shroud 19, are thus definitely avloided, and the power capability of the apparat-us markedly increased.

In summary, therefore, it is one major achievement of the present method and apparatus to provide a relatively large-diameter (slightly constricted) vortex-stabilized arc or discharge 27h which is surprisingly stable, and which produces a spectral emission in the nature oef infrared. Such a large-diameter discharge 27h is achieved despite the fact that the pressure in the arc chamber 17 is very high, for example 18 atmospheres. The indicated desired discharge is achieved, as stated above, by providing a major (at least 50 percent) gas ow through only the peripheral regions ofthe arc chamber 17 and a sufficiently minor amount of 4gas ow through one or more regions adjacent the terminal portions or portion of the arc 27b.

In accordance with anothermajor achievement of the present method and apparatus, it is possible to shift between the small-'diameter of highly constricted mode of operation (producing discharge 27a) and the lange-diameter or less constricted mode (producing discharge 27b) in an extremely s'hort period of time, and without changing the pressure in the entire system. Thus, the light source becomes a multi-purpose source which is readily shifted from one mode of operation to the other by merely changing the settings of various Valves.

Tlhe foregoing detailed description is to be clearly 'understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims.

We claim:

1. A radiation source, which comprises:

wall means to define a chamber,

said wall means having a portion formed of a material adapted to transmit light and similar radiation from said chamber,

electrode means to generate an electrical discharge in said chamber,

means to introduce gas continuously into said chamber and to effect vortical flow of said gas in said chamber about an axis extending between discharge portions of said electrode means,

means to drain at least half of said gas from said chamber at a region remote from said axis,

said drain means being so located that gas before draining therethrough will flow closely adjacent said transmissive material for effective gascooling thereof, and means to drain less than half of said gas from said chamber at at least one region relatively adjacent said axis.

2. The invention as claimed in claim 1, in which said transmissive material is in a region of said wall means defining a surface of revolution about said axis, and in which said first-named drain means communicates with said chamber adjacent said surface of revolution.

3. The invention as claimed in claim 1, in which said last-named drain means includes a passage through one of said discharge portions and communicating with said chamber adjacent said axis.

4. The invention as claimed in claim 1, in which said last-named drain means includes a passage through a shroud around one of said discharge portions.

5. The invention as claimed in claim 2, in which said gas-introduction means communicates with said chamber at one end thereof, and said first-named drain means communicates with said chamber at the other end thereof.

6. The invention as claimed in claim 1, in which a pulse source is connected across said electrode means to generate said discharge in the form of a spark.

7. F[lhe invention as claimed in claim 1, in which a D.C. source is connected across said electrode means to generate said discharge in the form of an electric arc.

8. A method of generating light and similar radiation, which comprises:

defining a chamber having a wall portion formed of a material adapted to transmit light and similar radiation from said chamber,

providing in said chamber the discharge regions of two electrode elements,

effecting continuous introduction of high-pressure gas into said chamber and vortical flow of at least a substantial proportion of said gas about an axis extended between said discharge regions of said electrode elements,

effecting between said discharge regions and in said chamber an electrical discharge,

draining from said chamber and at a region remote from said axis and adjacent said light-transmissive material a major proportion of the gas introduced into said chamber, and

draining from said chamber at a region relatively adjacent said axis a minor proportion of said gas which is introduced into said chamber.

9. The invention as claimed in claim 8, in which said last-named step comprises draining at said region adjacent said axis a sufiicient amount of gas that said discharge is highly constricted and produces a spectral emission high in the ultraviolet range.

10. The invention as claimed in claim 8, in which said last-named step comprises draining at said region adjacent said axis a sufficiently small amount of gas that said discharge is only slightly constricted and produces a spectral emission high in the infrared range.

11. The invention as claimed in claim 8, in which said method further comprises performing said last-named draining step by draining gas from said chamber through an opening formed in one of said discharge regions at said axis, and draining gas from said chamber through an annular passage around the other of said discharge regions.

12. The invention as claimed in claim 11, in which said method comprises effecting said electrical discharge in the form of a D.C. arc wherein said one discharge region is the anode.

13. The invention as claimed in claim 8, in which said method comprises effecting said electrical discharge in the form of a spark.

14. A multi-mode recirculating radiation source adapted to generate different spectral emission patterns without changing the gas pressure in the entire system, which comprises:

wall means to define a chamber,

said wall means having a window portion formed of light-transmissive material,

a recirculating gas system communicating with said chamber to effect continuous flow of high-pressure gas therethrough,

said system including inlet means to introduce high-pressure gas continuously into said charnber for vortical flow therein about a predetermined axis, said system further including drain means to withdraw gas continuously from said chamber and then recirculate at least a major portion of said gas back to said inlet means,

means to effect a high-current electrical discharge in said chamber along said axis, and

means associated with said recirculating gas system to cause said drain means to withdraw a sufficiently large proportion of the gas rpresent in said chamber from a region thereof remote from said axis and adjacent said window that the spectral emission pattern resulting from said discharge is largely in the nature of infrared,

said last-named means being controllable to cause said drain means to withdraw a sufficiently large proportion of the gas present in said chamber from a region thereof relatively adjacent said axis that the spectral emission pattern resulting from said discharge is largely in the nature of ultraviolet.

15. The invention as claimed in claim 14, in which said drain means includes a first gas-outlet passage communicating with said chamber at a region thereof remote from said axis and adjacent said window, and a second gas-outlet passage communicating with said chamber at a region thereof adjacent said passage, and in which said last-named means includes valve means to control the relative gas fiows in said first and second gas-outlet passages.

16. The invention as claimed in claim 14, in which said means to effect a high-current electrical discharge comprises a D.C. current source and first and second electrodes having arcing portions disposed in said chamber along said axis.

17. The invention as claimed in claim 14, in which said means to effect a high-current electrical discharge includes a pulse source and first and second electrodes having sparking portions disposed in said chamber along said axis.

18. The invention as claimed in claim 14, in which said wall means defines a surface of revolution about said axis, in which said wall portion formed of lighttransmissive material is in said surface of revolution, in which said means to effect a high-current electrical discharge includes first and second electrodes having arcing portions disposed in said chamber along said axis, one of said electrodes having a shroud therearound, in which said inlet means communicates with said chamber at a region relatively remote from said axis and in a generally tangential manner whereby to effect vortical flow of gas in said chamber about said axis, in which said drain means includes a first gas-outlet passage communicating with said chamber adjacent said surface of revolution, a second gas-outlet passage communicating with the space between said shroud and said one electrode, and a third gas-outlet passage communicating with an opening formed in the arcing portion of the other of said electrodes at said axis, and in which said last-named means comprises valve means to control the relative flows of gas through said passages.

19. The invention as claimed in claim 18, in which a high-current D.C. source is connected to said electrodes, in which the polarity of said source is such that said one electrode is the cathode, and in which said inlet means communicates with said chamber at a region radially outwardly of said other electrode.

20. The invention as claimed in claim 19, in which said first gas outlet passage communicates with said chamber at a region radially-outwardly of said shroud, and in which said inlet means has an axial component effecting helical fiow of said gas in said chamber.

21. A method of generating radiation in the general nature of light and in such manner that the spectral emission pattern is instantly changeable, which comprises:

providing a radiation source including spaced electrode portions enclosed within a chamber having a lighttransmissive wall portion, said source further including recirculation means to drain gas continuously from said source and then recirculate gas back t0 said source,

effecting an electrical discharge between said electrode portions, and

controlling the spectral emission pattern resulting from said electrical discharge by varying the proportion of gas drained from the peripheral region of said chamber in comparison to the proportion of gas drained from the central region of said chamber.

22. The invention as claimed in claim 21, in which said method further comprises effecting draining lof gas from the central region of said chamber at all times, and varying the proportion of gas drained from the region of said chamber remote from said central region.

23. A method of generating radiation in the general nature of light and in such manner that the spectral emission pattern is instantly changeable, which comprises:

pnoviding a radiation source including first and second spaced electrode portions enclosed within a chamber having a light-transmissive Wall portion, said source further including recirculation means to drain gas continuously from said source and then recirculate gas back to said source,

effecting an electrical discharge between said electrode portions,

effecting gas-vortex stabilization lof said discharge by gas flowing through said chamber, and

controlling the spectral emission pattern resulting from said electrical discharge by varying the proportion of gas drained from the peripheral region of said chamber in comparison to the proportion of gas drained from the central region of said chamber.

24. The invention as claimed in claim 23, in which said method further comprises providing said first electrode portion with a bore at Ithe axis of the vorticallyflowing gas effecting said gas-vortex stabilization, draining gas from said chamber through said axial bore, and varying the flow of gas through said axial bore in order to effect variation of said spectral emission pattern.

25. The invention as claimed in claim 24, in which said method further comprises draining through said axial bore only a small proportion of the gas drained from said chamber by said recirculation means.

26. The invention as claimed in claim 24, in which said method further comprises making said first electrode portion the anode.

References Cited UNITED STATES PATENTS 3,064,153 11/1962 Gage 313-231 X 3,255,379 6/1966 Miller 313-231 X 3,292,028 12/1966 Van Ornurn 313-231 X JAMES W. LAWRENCE, Primary Examiner.

P. C. DEMCO, Assistant Examiner.

U.S. Cl. X.R. 

